Need a mug/cup for cutting the lawn

I know this probably sounds insane. My dream has been to get a “one or two drink lawn.” I got that with 1.5 acres. My issue is I like to drink Vodka and diet coke/pepsi/soda/whateverthefuckyoucallitwhereyoulive. I obviously can’t have a cup with no top because it will spill out of the top. I have tried three different cups, but the issue is the carbonation. Of course while mowing, it builds up pressure and when I open the top, it explodes.

I have no idea if there’s even a solution to my problem but I figured this would be the place to go to. I don’t know why I drink vodka and diet other than I like the flavor. It’s just what I’ve drank forever. Any ideas? I’m thinking the answer is just as simple as getting a huge cup, filling it like 1/8 of the way up, and it having a breather. I have no idea, I just cut the lawn at my wife’s house that I live at.